Cutting tool for working the interior and exterior contours of workpieces

ABSTRACT

A cutting tool of the specified type is to be miniaturized and configured in such a manner that it is suitable for working bores having a diameter of 6 mm and more and for high-speed work with revolving tools. 
     The solution according to the invention provides that the adjustment screws for radially adjusting the cutting plate simultaneously form a clamping means for the form-locking clamping of the cutting plate to the supporting shoulder of the basic tool body. 
     A preferred field of use are precision drills and grinding tools equipped with inserted cutting strips made of a highly wear resistant cutting material.

BACKGROUND OF THE INVENTION

The invention is based on a cutting tool for working interior andexterior contours of workpieces, with the tool including at least onecutting plate exchangeably fastened to a basic tool body and beingadjustable radially to the tool axis by means of at least one adjustmentscrew while being clampable by clamping means to a supporting shoulderof the basic tool body that absorbs the working pressure. In a prior artcutting tool of this type (German Patent 3,201,508), a separate screwelement is provided to adjust the cutting plate and to clamp it tightlyinto the supporting shoulder of the basic tool body. The cutting plateis disposed at a clamping shoe which is supported in the basic tool bodyso as to be rotatable about an axis that is axially and radially offsetrelative to the cutting plate. The radial adjustment of the cuttingplate relative to the tool axis is effected by rotating the clampingshoe relative to the basic tool body, with this inevitably also changingthe angular position of the cutting plate relative to the tool axis. Toclamp the cutting plate or cutting edge to the supporting shoulder ofthe basic tool body, the clamping shoe is pulled at a right angleagainst the supporting shoulder, whereupon the cutting plate is held atthe basic tool body by a friction lock. This configuration requires arelatively large amount of space and is therefore unsuitable for toolswith which very small bores are to be worked. Moreover, the prior artarrangement is also unsuitable for high-speed work because the cuttingplate is not held in a form lock at the basic tool body to prevent itfrom radially escaping from the revolving tool.

SUMMARY OF THE INVENTION

The arrangement according to the invention concerns a cutting tool ofthe type discussed above where the radial adjustment of the cuttingplate with respect to the tool axis, together with the clamping of thecutting plate to a supporting shoulder of the basic tool body, aresimultaneously effected by means of at least one adjustment screw. Theinvention is thus distinguished by a particularly compact configurationin which, in principle, only one adjustment screw is required foradjustments and only one clamping nut for clamping in the cutting plate,and which therefore opens up the possibility of miniaturizing the tooland using it for precision working of small diameter bores.

Various advantageous modifications of the basic arrangement according tothe invention likewise are disclosed.

A form locking fastening of the cutting plate to the basic tool body canbe realized according to an advantageous embodiment of the invention ifthe tool is constructed with the following features: (a) the adjustmentscrew is disposed at an acute angle relative to the supporting shoulderof the basic tool body and engages in a clamping nut which is rotatablymounted on the basic tool body but is axially supported in onedirection; (b) the adjustment screw is provided with an axial clampingshoulder facing the angle vertex and urged against an axialcounter-shoulder facing the opening of the angle on the cutting plate incontact with the supporting shoulder; and (c) the adjustment screw isprovided with a longitudinal section that is arranged eccentric to thescrew axis while its eccentric circumferential face forms a radialclamping shoulder which presses against a radial counter-shoulderextending parallel to the screw axis on the cutting plate lying againstthe supporting shoulder. A tool of such a configuration is suitable forhigh-speed work because the centrifugal force acting on the cutting edgewhen the tool is revolving acts against the axial clamping shoulder ofthe adjustment screw so that the form lock is reliably retained. Thecutting plate can be given such a configuration that the centrifugalforce vector acting on its center of gravity goes through the region ofthe supporting shoulder of the basic tool body. There further resultsthe advantage that after release of the clamping nut, the cutting plateflips out of the plate seat and can be removed without it beingnecessary to remove the adjustment screws and clamping nuts completelyfrom the basic tool body.

According to preferred features of the invention, the clamping nut isdisposed at the end of the adjustment screw associated with the anglevertex and is axially supported at the basic tool body in the directionof the angle opening; the clamping nut is mounted in an outwardly opencylindrical recess of the basic tool body; and the axial clampingshoulder of the adjustment screw is formed at the transition of a screwhead provided with engagement surfaces for an adjustment tool to aneccentric shaft section forming the radial clamping shoulder. Thesefeatures result in a tool in which the adjustment screw and the clampingnut are easily accessible and which therefore can be manipulated withparticular ease during the exchange, adjustment and tightening of acutting plate.

The cutting plate can be secured against rotation about an axisperpendicular to the supporting shoulder of the basic tool body, forexample, by the provision of shoulders at the basic tool body whichcoact with the end faces of the cutting plate. However, particularly inconnection with longer cutting plates, it may be of advantage to providetwo adjustment screws next to one another to adjust and clamp in thecutting plate. In that case, different adjustments of the adjustmentscrews permits the cutting edge of the cutting plate to be set, withinlimits, at an angle to the tool axis.

For tools for working stepped bores, it is possible to advantageouslyrealize an axial setting of the cutting plate by providing an adjustmentelement for adjusting the cutting plate in the axial direction, with theadjustment element being supported in the basic tool body so as to berotatable therein transversely to the longitudinal extent of the basictool body, and a conversion element which converts the transversemovement into a longitudinal movement.

BRIEF DESCRIPTION OF THE DRAWINGS

One embodiment of the invention is illustrated to an enlarged scale inthe drawing figures and will be described in greater detail below.

FIG. 1 is a top plan view of a grinding tool or fine drilling toolincluding a cutting plate that is adjusted and fastened by twoadjustment screws;

FIG. 2 is a side elevational view of the tool of FIG. 1;

FIG. 3 is a sectional view along line III--III of FIG. 2;

FIG. 4 is a sectional view through the drill rod of the tool along lineIV--IV of FIG. 1;

FIG. 5 is a top plan view of the cutting plate of the drill; and

FIG. 6 is a sectional view along line VI--VI of FIG. 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The tool has as its basic body a drill rod 10 whose front end section 12is provided with a flattened portion 14 and carries a cutting plate 16which is exchangeably fastened to drill rod 10 by the means to bedescribed below. Cutting plate 16 is configured as a carrier for acutting strip 18 of a highly wear resistant material that is fastened tocutting plate 16 rigidly or possibly also exchangeably, for example byway of a dovetail guide. However, cutting plate 16 could also itself bemade of a wear resistant material and directly form the cutting strip orbe provided with a cutting edge 20.

In the region of flattened portion 14, drill rod 10 is provided with arecess 22 (FIG. 4) which begins in the cross-sectional plane 24 (FIG. 1)of drill rod 10 and extends to its front end. Recess 22 is delimited bya longitudinal wall 28 that lies at least approximately in a diagonalplane 26 and, on the other side, by a longitudinal wall 30 disposed atan acute angle a to diagonal plane 26 while forming a supportingshoulder for cutting plate 16. In addition to the elongate recess 22,the cross-sectional planes 32 and 34 (FIG. 1) of drill rod 10 are eachprovided with a passage 36 that starts at flattened portion 14 and endsat the opposite circumferential wall of drill rod 10. Above the bottomwall 38 of recess 22, the passage is provided with a semi-cylindricalsection 40 of a larger diameter and subsequent thereto with asemi-cylindrical section 42 of a smaller diameter. Below bottom wall 38,the passage forms a fully cylindrical bore section 44. At a clampingshoulder 46, the latter changes into the semi-cylindrical section 42 ofpassage 36.

Cutting plate 16 is a prismatic body defined in the longitudinaldirection, among others, by two side walls 48, 50 that are arranged atthe same angle a relative to one another as the longitudinal walls 28,30 of recess 22 in drill rod 10. At two locations whose axial distancecorresponds to the distance between the two cross-sectional planes 32,34 of drill rod 10, cutting plate 16 is provided with semi-cylindricalrecesses 52 which extend from the top down to a clamping shoulder 54.The radius of recesses 52 corresponds to the radius of sections 40 ofpassages 36 in drill rod 10 so that, once cutting plate 16 has beeninserted into the recess 22 of drill rod 10 and its side wall 50 liesagainst the longitudinal wall 30 of recess 22, pairs of oppositelydisposed sections 40 and recesses 52 supplement one another to formcylindrical pockets.

To adjust and clamp in cutting plate 16, two adjustment screws 60 areprovided which each include a head 62, a concentrically arrangedthreaded section 64 and an eccentric shaft section 66 therebetween,which changes at the top at an annular shoulder 68 into head 62 andwhose eccentric circumferential face forms a clamping shoulder 69.Threaded section 64 engages in a clamping nut 70 that is rotatablymounted in bore section 44 of passage 36 and is supported at clampingshoulder 46. A recess 72 is provided in the head 62 of each adjustmentscrew 60 for the mating engagement of a hexagonal key; at their lowerinner edges, clamping nuts 70 are likewise provided with engagementsurfaces 74 for a tool to turn the clamping nuts. An adjustment orelement screw 76 is provided to axially displace cutting plate 16. Thisscrew is mounted in a threaded bore disposed transversely to the toolaxis 78 and pushes by way of a ball 80 against cutting plate 16.

In the region of cutting plate 16, drill rod 10 is provided with twoguide strips 82a and 82b which, like cutting edge 20, radially slightlyproject beyond the exterior surface of drill rod 10 and guide drill rod10 in the bore. A guide strip 82b disposed diametrally opposite cuttingedge 20 additionally determines, by way of its distance from cuttingedge 20, the diameter of the bore to be produced. By way of a guidestrip 82a, the working pressure is absorbed and is transferred directlyto the workpiece. Instead of employing guide strips, individualcircumferential sections of the drill rod itself formed betweensegment-like ground surfaces at drill rod 10 may provide the guidance.Channels 84, 86 are provided in drill rod 10 for the supply of coolantto cutting strip 18 and for the removal of chips.

In order to insert, adjust and clamp in cutting plate 16, the twoadjustment screws 60 are initially turned upward, while holding on toclamping nuts 70, until cutting plate 16 is pivoted underneath the heads62 of adjustment screws 60 and can be placed against the longitudinalwall 30 of drill rod 10 forming the supporting shoulder. Then, theheight position of cutting plate 16 relative to longitudinal wall 30 andthus the radial distance of cutting edge 20 from the tool axis, andpossibly also the angle relative to the tool axis, can be varied and setto desired values by rotation of adjustment screws 60. Theses values area function of the radial distances of the clamping shoulders 69 formedat the eccentric shaft sections 66 of adjustment screws 60 from thescrew axes (diagonal plane 26, FIG. 4), which push cutting plate 16 moreor less far away from the screw axes to thus displace it upwardly onlongitudinal wall 30.

To adjust or preset the desired position of the cutting strip relativeto the tool axis, drill rod 10 may be held between the two tips of anadjustment device that engages in the two openings of channel 84 and theset dimension can be checked by means of two measuring gauges. Ifadjustment screws 60 have been brought into the prescribed rotaryposition, clamping nuts 70 are tightened while holding on to adjustmentscrews 60. This causes the axial clamping shoulders 68 at adjustmentscrews 60 to urge cutting plate 16 firmly against the longitudinal wall30 of drill rod 10. The center of gravity of cutting plate 16 togetherwith cutting strip 18, indicated in FIG. 3 by the point M, is selectedso that the centrifugal force vector acting on it passes through theregion of the longitudinal wall 30 of drill rod 10.

As an adjustment aid, markers may be provided at adjustment screws 60and at the surface regions of drill rod 10 surrounding the screws.Moreover, stops may be provided at adjustment screws 60 and on drill rod10 so as to delimit the adjustment range of adjustment screws 60.

The fastening of the cutting plate according to the invention may ofcourse also be provided for multiple and stepped tools for thesimultaneous working of interior and exterior contours of workpieces.

We claim:
 1. A cutting tool for working the interior and exteriorcontours of workpieces, with said tool comprising at least one cuttingplate exchangeably fastened to a basic tool body and being adjustableradially to the tool axis by means of an adjustment screw, while beingclampable by clamping means to a supporting shoulder of the basic toolbody that absorbs the working pressure, and wherein, for radialadjustment of the cutting plate, the adjustment screw simultaneouslyconstitutes a clamping means for clamping the cutting plate tightly tothe supporting shoulder of the basic tool body and has the followingfeatures:(a) the adjustment screw is disposed at an acute angle relativeto the supporting shoulder of the basic tool body and engages in aclamping nut which is rotatably mounted on the basic tool body but isaxially supported in one direction; (b) the adjustment screw is providedwith an axial clamping shoulder facing the vertex of the acute angle andurged against an axial counter-shoulder facing the opening of the angleon the cutting plate in contact with the supporting shoulder; and (c)the adjustment screw is provided with a longitudinal section that isarranged eccentric to the screw axis while its eccentric circumferentialface forms a radial clamping shoulder which presses against a radialcounter-shoulder extending parallel to the screw axis on the cuttingplate lying against the supporting shoulder.
 2. A cutting tool accordingto claim 1, wherein the clamping nut is disposed at an end of theadjustment screw associated with the vertex of the acute angle, and isaxially supported at the basic tool body in the direction of the angleopening.
 3. A cutting tool according to claim 2, wherein the clampingnut is mounted in an outwardly open cylindrical recess of the basic toolbody.
 4. A cutting tool according to claim 1 wherein the axial clampingshoulder of the adjustment screw is formed at a transition of a screwhead which is provided with engagement surfaces for an adjustment tool,to an eccentric shaft section forming the radial clamping shoulder.
 5. Acutting tool according to claim 1, wherein the cutting plate iselongated, and two juxtaposed adjustment screws are provided to adjustand clamp in the elongated cutting plate.
 6. A cutting tool according toclaim 1, wherein the cutting plate is adjustable in the axial directionby way of an adjustment element which is supported in the basic toolbody so as to be rotatable therein transversely to the longitudinalextent of the basic tool body, and a conversion element which convertsthe transverse movement into a longitudinal movement.
 7. A cutting toolaccording to claim 6, wherein said adjustment element is a screw andsaid conversion element is a ball.
 8. A cutting tool for working theinterior and exterior contours of workpieces, with said tool comprisingat least one cutting plate exchangeably fastened to a basic tool bodyand being adjustable radially to the tool axis by means of at least oneadjustment screw, while being clampable by clamping means to asupporting shoulder of the basic tool body that absorbs the workingpressure, and wherein: for radial adjustment of the cutting plate, theat least one adjustment screw simultaneously constitutes a clampingmeans for clamping the cutting plate tightly to the supporting shoulderof the basic tool body; the cutting plate is elongated; and twojuxtaposed adjustment screws are provided to adjust and clamp in theelongated cutting plate.
 9. A cutting tool for working the interior andexterior contours of workpieces, with said tool comprising at least onecutting plate exchangeably fastened to a basic tool body and beingadjustable radially to the tool axis by means of an adjustment screw,while being clampable by clamping means to a supporting shoulder of thebasic tool body that absorbs the working pressure, and wherein: forradial adjustment of the cutting plate, the adjustment screwsimultaneously constitutes a clamping means for clamping the cuttingplate tightly to the supporting shoulder of the basic tool body; thecutting plate is adjustable in the axial direction by an adjustmentelement, which is supported in the basic tool body so as to be rotatabletherein transversely to the longitudinal extent of the basic tool body,and a conversion element, which converts the transverse movement into alongitudinal movement.
 10. A cutting tool according to claim 9, whereinsaid conversion element is a ball.